Various types of co-ordinate measuring machines are known: bridge measuring machines, horizontal-arm measuring machines, pillar measuring machines, etc. Each of these machines typically comprises a reference surface, a first carriage mobile with respect to the reference surface along a first axis, a second carriage carried by the first carriage and mobile with respect thereto along a second axis perpendicular to the first axis, and a measuring spindle carried by the second carriage and mobile with respect thereto along a third axis perpendicular to the first and second axes. The spindle is designed to carry a measuring tool, which is displaced in the measuring volume as a result of the combination of the motions along the three axes.
For example, in portal measuring machines the first carriage is mobile along a horizontal axis and comprises two uprights and a horizontal cross member that defines the second axis, which is also horizontal, on which the second carriage is mobile. The spindle is constituted by a column with vertical axis, mobile with respect to the second carriage along its own axis.
The mobile members of a measuring machine are generally driven by respective electric motors via respective transmission systems.
A transmission system for a mobile member of a measuring machine must be designed so as to prevent as much as possible transmission of vibrations to the mobile member. In addition, there must be prevented transmission of forces in a direction orthogonal to the axis of motion. Generally, this is obtained thanks to the good quality of the components (motor, pinions, pulleys, belts, etc.) and by means of a very precise alignment of the transmission system with respect to the direction of motion. The connection between the motor and the mobile member, in the direction of motion, is generally made in the most rigid way possible.